Methotrexate (MTX), an antimetabolite of folic acid (FA), administered at low doses for long-term periods is one of the most efficacious treatments for a number of autoimmune diseases. However, toxicities limit its clinical usefulness. We will enroll patients into a double-blind, placebo-controlled trial of 2 levels of FA supplementation in lessening toxicity & preserving efficacy of MTX.